The non-protein nitrogen portion of human milk represents approximately 25% of the total nitrogen containing compounds present in human milk. This fraction contains all of the newly discovered growth factors and other biologically functional components of these important fluids. This project will focus in two areas: 1) A longitudinal study will be performed to analyze known whey proteins by immunological methods. Glycoproteins will be isolated as a group, then separated into individual components and quantitated. Metalloproteins will be isolated in groups, separated and quantitated. Vitamin-binding proteins will be quantitated. Unknown whey proteins will be isolated, identified and quantitated. 2) Methods for isolating NPN compounds will be developed and evaluated. Post-prandial, diurnal and longitudinal variations in known individual NPN compounds will be determined. Unknown NPN compounds will be separated by chromatographic techniques, quantitated with regard to nitrogen content and characterized.